AVRO timestamp parsing in Nifi

[#1]

Hitting a weird issue in Nifi that I can't get my head around.

I am consuming AVRO records from Kafka with a timestamp field. The definition is

    {
      "name" : "timestamp",
      "type" : {
        "type" : "long",
        "logicalType" : "timestamp-millis"
      }
    },

If I use a JSON record writer then in the queue viewer I can see the field contains the original long value. However if I use an AVRO writer the field is formatted as a date/time value, e.g. 2025-09-26T15:29:44.466Z.

I assumed this was just pretty-printing in the queue viewer. But if I then send those flowfiles to a ConvertRecord process with an AVRO reader and a FreeText writer the timestamp field is now displayed as YYYY-mm-DD HH:MM:SS. Which means I've lost precision and I need to use expression language to re-parse the field to convert it back to a long value.

So, I'm forced to us JSON as the intermediary format. If I use AVRO I loose precision.

This is Nifi 2.5.

[#2]

Reading back my post I didn't explain it very well.

When I output a timestamp field using a FreeFormTextRecordSetWriter the field is implicitly converted to a string of format YYYY-mm-DD HH:MM:SS. I cannot see any way to change this behaviour and all my searches turn up blank. What I want is the Writer to respect the original long value.